Generally, an aluminum alloy heat exchange device with aluminum alloy fins and aluminum alloy heat exchange tubes brazed thereon is used widely, and furthermore, in order to increase the heat exchange rate, an extruded flat tubed strip as a heat exchanging tubes formed by extrusion of aluminum alloy material is often used.
In order to manufacture a heat exchange device structured in such a manner as above, as a method of coating metallic particles for making a brazed connection on the surface of a body, for instance, an extruded flat tubed strip used as a heat exhange device, there is known generally a method of turning the metallic particles into a slurry by using water or a solvent and binder and coating with this slurry by spraying with a spray gun. Furthermore, other coating methods such as brushing and screen printing are known.
However, the method of spraying with a spray gun suffers from bad coating efficiency because coating is conducted by moving the spray gun over the surface of the body, and furthermore, the spray gun itself may become clogged up. On the other hand, the coating method of brushing or screen printing is not amenable for continuous coating.
Moreover, since volatile solvents are made of organic medium and most often poisonous, there is a need to be cautious, and consequently, solvents such as these are not used very much. Also, other than the volatile solvent, there is a need to preheat the extruded flat tubed strip. When the preheating temperature is low, the sticking of slurry is prevented, and this causes the slurry to drip, and if the temperature is too high, the deposited slurry is repelled and this causes problems with the coating process. Therefore, there are problems such as a high demand for temperature control of a coating body, that is, a body to be coated, as well as enlargement and increased complexity of the pertinent facility.